AC-to-AC converters adjust power parameters for specialized equipment. They convert standard grid power (like 120V at 60Hz) to a different voltage or frequency. While not found inside vehicles, they are common in shop machinery like variable-frequency drives for air compressors.
In industrial settings, they run heavy three-phase motors from single-phase utility power. This allows shops to use heavy equipment without installing expensive three-phase power lines. They also regulate voltage to protect sensitive shop diagnostics tools.
Some EV charging stations use these converters to manage grid power. They align utility voltages with the station's transformers, keeping charging speeds steady during peak grid demand.